Altitudinal patterns of woody vegetation diversity in Al-Jabal Al-Akhdar, a Mediterranean mountain

This study examines the floristic composition, structural attributes, diversity patterns, and distribution ofendemic woody species along analtitudinal gradient inthe Al-Jabal Al-Akhdar mountain ofnortheastern Libya. Stratified sampling was conducted across four elevation zones onthe northern and southern slopes. Phytosociological parameters – including density, basal area, importance value index, and diversity indices – were assessed, and Pearson correlations were used toevaluate relationships with altitude and aspect. Atotal of61 woody species from 43 genera and 26 families were recorded, highlighting the region's biodiversity. Tree and shrub density and basal area increased with elevation, particularly onnorthern slopes. Juniperus phoenicea L. emerged asthe most dominant tree, while Phlomis floccosaD.Don and Pistacia lentiscus L. dominated the shrub layer. Diversity indices showed negative correlations with altitude, indicating declining species richness and evenness at higher elevations under cooler temperatures and greater environmental stress. Ten endemic woody species were documented, with endemic richness positively associated with altitude, reflecting the role of habitat isolation and environmental filtering. These findings provide essential insights for biodiversity conservation, climate adaptation, and ecosystem management in Al-Jabal Al-Akhdar and comparable mountainous ecosystems.